Field of the Invention
The present invention relates to a carrier junction system, and more particularly, to a method and apparatus for monitoring a physical downlink control channel (PDCCH) in a carrier junction system.
Discussion of the Related Art
In the following description, 3GPP LTE (3rd generation partnership projecting long term evolution, hereinafter abbreviated LTE) and 3GPP LTE-Advanced (hereinafter abbreviated LTE-A) communication systems are schematically explained as an example of a mobile communication system to which the present invention is applicable.
At least one cell exists in one eNode B. The cell is set to one of bandwidths including 1.25 MHz, 2.5 MHz, 5 MHz. 10 MHz, 15 MHz, 20 MHz and the like and then provides an uplink or downlink transmission service to a plurality of user equipments. Different cells can be set to provide different bandwidths, respectively. The eNode B controls data transmission and reception for a plurality of user equipments. The eNode B sends downlink scheduling information on downlink (DL) data to inform a corresponding user equipment of time/frequency region for transmitting data to the corresponding user equipment, coding, data size, HARQ (hybrid automatic repeat and request) relevant information and the like. In addition, the eNode B sends uplink scheduling information on uplink (UL) data to a corresponding user equipment to inform the corresponding user equipment of a time/frequency region available for the corresponding user equipment, coding, data size, relevant HARQ information and the like. An interface for user or control traffic transmission is usable between eNode Bs.
Wireless communication technology has been developed up to LTE based on WCDMA (wideband code division multiple access) but the demands and expectations of users and service providers are continuously rising. Since other radio access technologies are continuously developed, new technological evolution is required to remain competitive in the future. For this, reduction of cost per bit, service availability increase, flexible frequency band use, simple-structure and open interface, reasonable power consumption of user equipment and the like are required.
Recently, 3GPP is working on standardization of the next technology for LTE. In the present specification of the present invention, the next technology shall be named ‘LTE-Advanced’ or ‘LTE-A’. Major differences between the LTE system and the LTE-A system lie in system bandwidth difference and relay introduction.
The LTE-A system has a goal of supporting a maximum broadband of 100 MHz. For this, the LTE-A system uses carrier aggregation or bandwidth aggregation to achieve a broadband using a plurality of frequency blocks. Carrier aggregation enables a plurality of frequency blocks to be used as one large logical frequency band to use a wider frequency band. A bandwidth of each frequency block can be defined based on a system block used by the LTE system. In addition, each frequency block is transmitted using a component carrier.
As a carrier aggregation technology is adopted in LTE-A, which is a next-generation communication technology, there is a need for a method for receiving, by a user equipment, a signal from an eNode B or a relay in a system which supports a plurality of carriers.